Military techniques often include the deployment of a plurality of platforms or vehicles, such as armored vehicles in a terrestrial context, aircraft in an aerial environment, and ships in a naval context. Many, if not most, of these vehicles are equipped with one or more sensors for sensing the environment of the vehicle and for producing signals indicative of the presence of potential targets. As to any particular vehicle, its sensors may respond to other friendly vehicles and also to potentially unfriendly vehicles and other targets. It should be noted that in some contexts an individual may carry sensors and for this purpose may be considered to be a platform or vehicle.
The sensors of a group of vehicles (or vehicles and individuals) dispersed over a combat region will often gather more total information than any single vehicle alone, as the locations and capabilities of some of the sensors allows the sensed area to extend beyond the sensing range of many of the other sensors. For purposes of providing maximum information to each vehicle (and individual, if applicable), it is desirable to interconnect the vehicles so that the combined data from the group of sensors is available to each member of the group. Thus, the information from a sensor on a particular platform may be transmitted by way of an information path to another platform. This information may be about the location(s) of friendly vehicles or potentially unfriendly entities.
When information about entities in the environment (hereinafter targets) is received over a communication channel from a sensor on another vehicle, the information must be correlated with the information sensed by the own-vehicle sensors. If correlation is not performed, the possibility exists that each of several remote sensors will sense the same target, but, due to unavoidable inaccuracies among the coordinate systems of the various sensors or vehicles, at disparate locations. It is easy to understand that this can be very disadvantageous, as a single hostile target sensed by many friendly forces might be incorrectly interpreted as being a swarm of hostiles, each at a slightly different location. This, in turn, might lead to the unnecessary launching of a large number of countermeasure missiles, when there is but a single target. In addition, since the target's actual location appears differently at each of the friendly vehicles, there is the potential for missing the target with many of the countermeasures.
A conventional way to correlate the coordinate systems is to correlate the own-vehicle sensor targets with the ones identified by other vehicles. This can often be done seriatim, in that vehicles arrive at a particular gathering point sequentially, and the second to arrive can correlate its coordinate system to that of the first-to-arrive by gridlock techniques. Gridlock techniques involve the assumption that targets in an area should appear in the sensor data of both sources. Mathematical transformations can be performed at one of the platforms to minimize the errors between the remotely reported locations of the targets and the locally reported locations of the targets.
FIG. 1 is a plan view of a portion 10 of a sea surface 12 in which several platforms in the form of ships are disposed. In FIG. 1, a flotilla 14 of friendly platforms includes ships 16, 18, and 20. Ships 16, 18, and 20 each bear sensors, such as radar, infrared sensors, optical sensors, or the like, which sense the presence of the other ships of flotilla 14, and which also sense the presence of aircraft in the vicinity, represented by an aircraft 22. The sensing of aircraft such as 22 by the platforms of flotilla 14 is represented in FIG. 1 by “lightning bolt” symbols 24 and 26. The ships 16, 18, and 20 of flotilla 14 communicate among themselves by means of a communication network N, inter-ship portions of which are designated by lightning bolt symbols N1, N2, and N3. It should be understood that the intership network N may include many different signal paths, which variously include digital and analog portions, portions which are encrypted and other portions of which are not encrypted, and which traverse various paths, possibly including a path extending through a satellite 36. It also should be understood that, while ships are principally illustrated as being nodes of the network, the network can include air, space, and land assets.
Each of the sensors of ships 16, 18, and 20 of flotilla 14 of FIG. 1 makes its own assessment of the sensor signals which its own sensors generate, and distribute the assessed information (or possibly some raw information from some sensors) over the network N among the ships of the flotilla. Thus, each ship of flotilla 14 has access to all the information from the various ships of the flotilla.
From the location of flotilla 14 of FIG. 1, a hostile ship 30 is over the horizon, and therefore may be invisible to the sensors of the flotilla 14. A friendly ship 32 is illustrated as being in the general vicinity of hostile ship 30, sufficiently so that its sensors can sense the hostile ship, as suggested by lightning bolt 34. Friendly ship 32 also senses aircraft 22 as represented by lightning bolt 38.
When friendly ship 32 “joins” the flotilla 14, as by joining network N, it is desirable that the information sensed by friendly ship 32 be made available over network N to the various ships 16, 18, and 20 of flotilla 14, and that the information sensed the ships of the flotilla be made available to friendly ship 32. When ship 32 joins the flotilla 14, additional “target” information is made available over the network to the various ships. It is desirable to quickly and accurately rationalize the coordinate systems of the flotilla and of friendly ship 32, so that the information which is “new” to each platform can be effectively used, as by orchestrating a response to the presence of hostile ship 30.